Method of treating foundry sands



Patented Sept. 28, 1943 UNITED STATES PATENT OFFICE METHOD OF TREATING FOUNDRY SANDS Joseph A. Gitzen, River Hills, Wis.

No Drawing. Application May 2, 1941, Serial No. 391,576

3 Claims.

ordinarily mixed as a binder to increase the form. sustaining qualities thereof.

With the various types of sand heretofore used, however, much difiiculty has been experienced due to the development of cracks in the molds, and more commonly in the cores, under the heat and pressure of the molten metal to which they are subjected. The cracks are objectionable because entry of the metal into them produces undesirable formations in the castings variously known as veining, feathers, nigger hair, spider webs, etc.

An object of the present invention is to eliminate the above difficulty. This I have accomplished by treating foundry sands in the manner hereinafter pointed out.

For purposes of illustration and explanation the invention will be hereinafter described as applied to core sands, although it is also applicable with like advantage to molding sands and mold facing sands.

In carrying out the present invention, small quantities of iron oxide, either alone or with various other substances, is added to and mixed with the sand. The sand may be of any of the various types heretofore employed for the purpose, and, after the above named substance has been added, it may be used in the production of molds or cores by any known or approved method. I have discovered that the addition of very little iron oxide to the sand is sufficient to render the resulting mold or core immune from the objectionable cracking above mentioned. I have successfully used ferric oxide for the purpose although ferrous oxide may also be used which like results. The iron oxide may be added directly to the sand or to the binding material employed in forming the mold or core.

The proportion of iron oxide to be added for best results is dependent upon the type of core sand used, the size of the core, and the thickness of the surrounding metal in the finished casting. If the sand is of a type containing impurities and the surrounding metal section is not too large, the addition of iron oxide in an amount equal to from to 1% by weight of the sand, will ordinarily prove sufi'icient to prevent cracking. With ordinary commercial core sands, however, which are normally quite free from impurities, a somewhat'greater percentage of iron oxide is ordinarily required, and percentages up to 6% may be used. The addition of iron oxide alone in percentag'es materially above 6% will ordinarily produce an objectionable condition in the casting commonly known as scabbing, in which parts of the core sand tenaciously adhere to the cast- Although the addition of iron oxide alone to core sands in the percentages above namedhas proven entirely satisfactory, I have found it advantageous to use certain other substances with it. For instance, I have found that a mixture of iron oxide and carbon may be used, and that .when this mixture is added to the core sanda smaller percentage is sufficient to prevent core cracking than if iron oxide alone were added. The iron oxide and carbon are preferably used in equal proportions, although the proportions are not'critical. Activated carbon is preferably used, although all other types, such as charcoal, pulverized coke or coal, carbon black, lamp black, N or graphites, both graphitie or amorphous may be employed.

Another mixture that may be advantageously employed as a core cracking preventative comprises iron oxide, ide, metallic aluminum, and carbon, preferably in substantially equal proportions although the particular proportions are not important. I have found that the addition of smaller proportions of this mixture to core sand is sufficient to prevent' core cracking than when iron oxide alone is added, and also that this mixture may be added to core sand in greater proportionsthan iron oxide alone without danger of scabbing. For instance, in'cores made from a common com mercial core sand known as Ottawa washed and dried Silica sand, I have found that an addition of 2% of iron oxide to that sand is required to prevent core cracking, and that the addition of (S produces scabbing, whereas the addition of only 1 /2 of this mixture is sufficient to prevent core cracking and as high as 8% has been used without producing scabbing.

Various changes may be made in the invention hereinabove specifically described without departing from or sacrificing the advantages of the invention as defined in the appended claims.

I claim:

1. The method of treating foundry sands which consists in mixing therewith a small amount of a mixture comprising iron oxide, chromium oxide, aluminum oxide, metallic aluminum, and carbon.

2. The method of treating foundry sands which consists in mixing therewith small quantitles of iron oxide, chromium oxide, metallic aluminum, and carbon.

3. A mixture adapted to be mixed with foundry sands, said mixture including substantially equal parts of iron oxide, chromium oxide, aluminum oxide, metallic aluminum,,and carbon;

JOSEPH A. GITZEN.

chromium oxide, aluminum ox- 

